I'd like to see a candidate that runs on the bring America together again platform, with BATA hats even. So far the moderates are in a better position for that than the progressives. And that means a higher probability of getting more done.
What decent bills does ANYONE realistically see Dem candidate x and Republicans working together on? Because I see almost none where it would realistically happen. An infrastructure bill maybe. And they could probably do that under Trump, if they wanted to (I do understand not wanting to help Trump, Republicans can play that game too though and have). Perhaps they could do something about opiates (but really again, even the Trump admin has passed some laws there). But even "moderate" Dems who want to expand the ACA would not get a compromise with Republicans who want to get rid of the ACA (it passed without a single Republican vote - so this shows how popular their positions will NOT be with Republican lawmakers - they will go nowhere there). And Obama wanted to compromise as much as anyone possibly could, but what came of it? So what exactly is going to get done with Dems and Republicans working together? You can't get anything done via compromising if only one side is willing to compromise, because compromise implies working together, not just giving one party everything they want and getting nothing. Better to just pick someone who won't win over the Republican lawmakers (none of them will), but if they don't have congress will do what they can with administrative staffing, executive orders etc. etc.. Afterall Trump does. And that can do some real good, whereas the capacity to achieve much through compromise seems quite limited.

For winning there is some case to be made a moderate might be better, it might be the over 65 vote that is needed to win (they are most likely to vote) and Biden and Buttigieg pull in older voters (Warren pulls some too). Most under 40 will yawn to the polls but they aren't as reliable voters anyway.